The Lipopolysaccharide of
            <i>Brucella abortus</i>
            BvrS/BvrR Mutants Contains Lipid A Modifications and Has Higher Affinity for Bactericidal Cationic Peptides

Manterola, Lorea; Moriyón, Ignacio; Moreno, Edgardo; Sola‐Landa, Alberto; Weiss, David S.; Koch, Michel H. J.; Howe, Jörg; Brandenburg, Klaus; López-Goñi, Ignacio

doi:10.1128/jb.187.16.5631-5639.2005

Cited by 77 publications

(89 citation statements)

References 66 publications

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“…In pathogenic bacterial species, two-component systems have evolved to sense AMP activity directly, along with other signals, and activation of these systems leads to changes in gene expression that increase AMP resistance (47). Whether the S. meliloti ExoS-ChvI and FeuP-FeuQ also sense AMPs directly and regulate important AMP-resistance functions is not yet known, but the ortholog of ExoS-ChvI in the animal pathogen Brucella abortus is required for AMP resistance (37). An intriguing possibility suggested by our results is that ExoS-ChvI and FeuP-FeuQ may use nodule cationic AMPs as signals to induce functions such as exopolysaccharides and cyclic glucans that are needed for infection.…”

Section: Discussionmentioning

confidence: 99%

“…RirA is a transcriptional repressor that regulates iron acquisition and metabolism genes. ExoS-ChvI and FeuPFeuQ signaling is required for S. meliloti symbiosis (32,34), and work on related pathogenic α-proteobacteria has determined that all three regulators have critical functions during host infection (35)(36)(37).…”

Section: Ncr247 and Other Cationic Peptides Activate Three Regulons Imentioning

confidence: 99%

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Host plant peptides elicit a transcriptional response to control theSinorhizobium meliloticell cycle during symbiosis

Penterman

Abo

Nisco

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

139

142

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The α-proteobacterium Sinorhizobium meliloti establishes a chronic intracellular infection during the symbiosis with its legume hosts. Within specialized host cells, S. meliloti differentiates into highly polyploid, enlarged nitrogen-fixing bacteroids. This differentiation is driven by host cells through the production of defensin-like peptides called "nodule-specific cysteine-rich" (NCR) peptides. Recent research has shown that synthesized NCR peptides exhibit antimicrobial activity at high concentrations but cause bacterial endoreduplication at sublethal concentrations. We leveraged synchronized S. meliloti populations to determine how treatment with a sublethal NCR peptide affects the cell cycle and physiology of bacteria at the molecular level. We found that at sublethal levels a representative NCR peptide specifically blocks cell division and antagonizes Z-ring function. Gene-expression profiling revealed that the cell division block was produced, in part, through the substantial transcriptional response elicited by sublethal NCR treatment that affected ∼15% of the genome. Expression of critical cell-cycle regulators, including ctrA, and cell division genes, including genes required for Z-ring function, were greatly attenuated in NCR-treated cells. In addition, our experiments identified important symbiosis functions and stress responses that are induced by sublethal levels of NCR peptides and other antimicrobial peptides. Several of these stress-response pathways also are found in related α-proteobacterial pathogens and might be used by S. meliloti to sense host cues during infection. Our data suggest a model in which, in addition to provoking stress responses, NCR peptides target intracellular regulatory pathways to drive S. meliloti endoreduplication and differentiation during symbiosis.rhizobia-legume | host-microbe interactions

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Section: Discussionmentioning

confidence: 99%

Section: Ncr247 and Other Cationic Peptides Activate Three Regulons Imentioning

confidence: 99%

Host plant peptides elicit a transcriptional response to control theSinorhizobium meliloticell cycle during symbiosis

Penterman

Abo

Nisco

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

139

142

View full text Add to dashboard Cite

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“…The limit of detection on bactenecin (5 × 10 4 cfu/ ml) was 10-fold higher than observed in two other rapid biosensor systems employing antibodies for detection [34,35], but 20-fold higher than an additional array-based method [22]. Not surprisingly, B. melitensis did not demonstrate any significant binding to immobilized cecropins, magainin-1, or melittin; the Brucella strain used in this study produces "smooth" lipopolysaccharide (LPS) and several researchers have documented that smooth strains of Brucella are significantly more resistant than rough strains to inactivation/killing by these specific AMPs [36][37][38]. Interestingly, B. melitensis bound to bactenecin to a higher extent than to polymyxin B in the present study, whereas Martinez de Tejada and coworkers [37] observed the opposite effect on viability; however, it has been demonstrated that AMP-membrane binding does not always result in cell killing [39].…”

Section: Discussionmentioning

confidence: 99%

Antimicrobial peptides as new recognition molecules for screening challenging species

Kulagina

Shaffer

Ligler

et al. 2007

Sensors and Actuators B: Chemical

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The goal of this study was to evaluate binding of four targets of biodefense interest to immobilized antimicrobial peptides (AMPs) in biosensor assays. Polymyxins B and E, melittin, cecropins A, B, and P, parasin, bactenecin and magainin-1, as well as control antibodies, were used as capture molecules for detection of Cy3-labeled Venezuelan equine encephalitis virus (VEE), vaccinia virus, C. burnetti and B. melitensis. Although VEE, vaccinia virus and C. burnetti did not show any binding activity to their corresponding capture antibodies, B. melitensis bound to immobilized antiBrucella monoclonal antibodies. The majority of the immobilized AMPs included in this study bound labeled VEE, vaccinia virus and C. burnetti in a concentration-dependent manner, and B. melitensis bound to polymyxin B, polymyxin E, and bactenecin. No binding was observed on immobilized magainin-1. In contrast to all bacterial targets tested to date, VEE and vaccinia virus demonstrated similar patterns of binding to all peptides. While the direct assay is generally replaced by a sandwich assay for analysis of real-world samples, direct binding experiments are commonly used to characterize specificity and sensitivity of binding molecules. In this case, they clearly demonstrate the capability of AMPs as recognition molecules for four biothreat agents.

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“…Neither mutant can survive within host cells and this might be because their outer membranes are compromised 82,160 . These mutants are also sensitive to detergents and to antimicrobial peptides, such as polymyxin B, that resemble defence compounds produced by phagocytic cells and plant cells 82,162,163 . LPS lipid A, with the appropriate structure, might also be important for the survival of S. meliloti and B. abortus within their respective hosts 83,158 .…”

Section: Box 3 Host Invasion Parallels Between Rhizobia and Animal Pamentioning

confidence: 99%

“…For example, the B. abortus bvrS/bvrR sensor kinase/response regulator system is required for intracellular survival 31,166 . The B. abortus bvrS/bvrR system may be required for virulence, because it controls the expression of several outer membrane proteins and is involved in modulating the properties of bacterial lipopolysaccharide 162,167 . It has not been possible to construct null mutants of the S. meliloti homologues of these genes, exoS and chvI, indicating that they are essential 32,168 .…”

Section: Box 3 Host Invasion Parallels Between Rhizobia and Animal Pamentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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Nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. Once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. Bacterial differentiation and nitrogen fixation are dependent on the microaerobic environment and other support factors provided by the plant. In return, the plant receives nitrogen from the bacteria, which allows it to grow in the absence of an external nitrogen source. Here, we review recent discoveries about the mutual recognition process that allows the model rhizobial symbiont Sinorhizobium meliloti to invade and differentiate inside its host plant alfalfa (Medicago sativa) and the model host plant barrel medic (Medicago truncatula).The recent completion of the Sinorhizobium meliloti genome sequence, and the progress towards the completion of the Medicago truncatula genome sequence, have led to a surge in the molecular characterization of the determinants that are involved in the development of the symbiosis between rhizobial bacteria and leguminous plants. Aromatic compounds from legumes called flavonoids first signal the rhizobial bacteria to produce lipochitooligosaccharide compounds called Nod factors 1 . Nod factors that are secreted by the bacteria activate multiple responses in the host plant that prepare the plant to receive the invading bacteria. Nod factors and symbiotic exopolysaccharides induce the plant to form infection threads, which are thin tubules filled with bacteria that penetrate into the plant cortical tissue and deliver the bacteria to their target cells. Plant cells in the inner cortex internalize the invading bacteria in host-membrane-bound compartments that mature into structures known Correspondence to G.C.W. gwalker@mit.edu. Competing interests statementThe authors declare no competing financial interests. DATABASES Invasion of plant rootsAlthough plant roots are exposed to various micro-organisms in the soil, their cell walls form a strong protective barrier against most harmful species. The early steps in the invasion of barrel medic (M. truncatula) and alfalfa (Medicago sativa) roots by S. meliloti are characterized by the reciprocal exchange of signals that allow the bacteria to use the plant root hair cells as a means of entry. Initial signal exchangeFlavonoid compounds (2-phenyl-1,4-benzopyrone derivatives) produced by leguminous plants are the first signals to be exchanged by host-rhizobial symbiont pairs 1 (FIG. 1). Flavonoids bind bacterial NodD proteins, which are members of the LysR family of transcriptional regulators, and activate these proteins to induce the transcription of rhizobial genes 1,2 . For example, the M. sativa-derived flavonoid luteolin stimulates binding of an active form of NodD1 to an S. meliloti 'nod-box' p...

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The Lipopolysaccharide of Brucella abortus BvrS/BvrR Mutants Contains Lipid A Modifications and Has Higher Affinity for Bactericidal Cationic Peptides

Cited by 77 publications

References 66 publications

Host plant peptides elicit a transcriptional response to control theSinorhizobium meliloticell cycle during symbiosis

Host plant peptides elicit a transcriptional response to control theSinorhizobium meliloticell cycle during symbiosis

Antimicrobial peptides as new recognition molecules for screening challenging species

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

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